improve diagnostics suggestion for missing `@` in slice id binding to rest pattern

add issue 72373 tests


fmt test


fix suggestion format

Replacement, not insertion of suggested string

implement review changes

refactor to span_suggestion_verbose, improve suggestion message,  change id @ pattern space formatting

fmt


fix diagnostics spacing between ident and @


refactor reference

1 files changed, 20 insertions, 0 deletions

diff --git a/src/librustc_parse/parser/mod.rs b/src/librustc_parse/parser/mod.rs
index b21524cb9bd..c00b6084829 100644
--- a/src/librustc_parse/parser/mod.rs
+++ b/src/librustc_parse/parser/mod.rs
@@ -672,6 +672,26 @@ impl<'a> Parser<'a> {
                                 }
                             }
 
+                            // If this was a missing `@` in a binding pattern
+                            // bail with a suggestion
+                            // https://github.com/rust-lang/rust/issues/72373
+                            if self.prev_token.is_ident() && &self.token.kind == &token::DotDot {
+                                let msg = format!(
+                                    "if you meant to bind the contents of \
+                                    the rest of the array pattern into `{}`, use `@`",
+                                    pprust::token_to_string(&self.prev_token)
+                                );
+                                expect_err
+                                    .span_suggestion_verbose(
+                                        self.prev_token.span.shrink_to_hi().until(self.token.span),
+                                        &msg,
+                                        " @ ".to_string(),
+                                        Applicability::MaybeIncorrect,
+                                    )
+                                    .emit();
+                                break;
+                            }
+
                             // Attempt to keep parsing if it was an omitted separator.
                             match f(self) {
                                 Ok(t) => {